1. Field of the Invention
The present invention relates to an object, a method, or a manufacturing method. In addition, the present invention relates to a process, a machine, manufacture, or a composition of matter. In particular, one embodiment of the present invention relates to a semiconductor device, a display device, a light-emitting device, a power storage device, an imaging device, a driving method thereof, or a manufacturing method thereof. In particular, one embodiment of the present invention relates to a secondary battery and a method for manufacturing the secondary battery.
2. Description of the Related Art
In recent years, wearable devices have been actively developed. Since wearable devices are worn on one's body, it is preferable that they have a shape along a curved surface of the body. Therefore, secondary batteries used in wearable devices are needed to be curved in the shape along a curved surface of the body and to have flexibility like displays and other housings.
For example, Patent Document 1 discloses a secondary battery which has a curved shape, and electronic devices including the secondary battery.
Important things in an improvement in reliability of a secondary battery are a positive electrode tab and a negative electrode tab, for example. Note that a positive electrode tab refers to a portion in a positive electrode; the portion extends to be electrically connected to a positive electrode lead and includes a region where an active material is not formed. A negative electrode tab refers to a portion in a negative electrode; the portion extends to be electrically connected to a negative electrode lead and includes a region where an active material is not formed. These portions mostly have elongated shapes and are likely to cause a crack, a breakage, or the like compared with a portion where an active material is formed.
For example, Patent Document 2 discloses a secondary battery where slits or the like are provided in tab portions to reduce metal fatigue of a positive electrode tab and a negative electrode tab.